Magnet pump with rear thrust bearing member

Abstract: A rear thrust bearing member (41) is disposed to be in frictional contact with an axial end face (42) of the spindle (34) supported in a cantilever fashion in the neighborhood of and on the rear side of an impeller (26). Frictional heat that is generated in this part is diffused satisfactorily with a cooling effect provided by the stirring of the impeller (26) in the pump casing and a heat diffusion effect provided by the circulating effect. Thus, the temperature rise of the frictional portions is suppressed, and adverse effects of heat on the surrounding member is prevented.

Description: Background of the invention This invention relates to a magnet pump including a front casing defining an inner pump chamber and having an axially extending suction port and a circumferentially extending discharge port, an impeller rotatably disposed in the pump chamber, the impeller having a front side portion facing the suction port and a rear side portion opposite to the front side portion, a cylindrical rear casing with a bottom cooperating with the front casing to enclose the pump chamber fluid tight, a drive rotor disposed outside the rear casing and having a drive magnet, a driven rotor having a driven magnet facing and forming a magnet coupling with the drive magnet and rotatable in unison with the impeller which is mounted on a front side portion of the driven rotor, a spindle secured to the rear casing, said spindle having an axial end face at the extended end portion axially projecting toward the suction port and rotatably supporting the driven rotor and the impeller thereon, and a rear thrust bearing member for supporting a rearward thrust acting on the driven rotor and the impeller in the direction opposite to the direction toward the suction port. A magnet pump of this type is known (GB-A-1 134 228). The driven unit of this magnet pump including the driven magnet covers a bearing member being permanently pressed to a point of a pivot bearing pin. This pin and the bearing member constitute the only bearing for the driven magnet and the impeller. The extended end portion is always engaged and received by the bearing member which always supports the rotating unit radially and axially. A prior art magnetic pump of this type has a structure as shown, for instance, in Fig. 3. The well-known magnet pump 1 as shown in Fig. 3 comprises a front casing having a suction port 3 extending in the axial direction as shown by axis line X-X and a discharge port 4 extending circumferentially, an impeller 6 rotationally disposed in the pump chamber 2 and having a front side portion (i.e., right side in the Figure), facing the suction port 2, a cylindrical rear casing with a bottom cooperating with the front casing 5 to enclose the pump chamber 2 liquid tight, a driven rotor 10 disposed outside the rear casing 7, having a ring-like drive magnet 8 and receiving a rotational drive torque from a drive motor (not shown). disposed in a pump body 9, a driven rotor 12 disposed in the rear casing 7, having a ring-like driven magnet 11 facing and forming a magnet coupling with the drive magnet 8 via the rear casing and rotatable in unison with the impeller, and a spindle 14 secured at the distal end thereof to the bottom 7a of the rear casing 7 via an integral boss 13 projecting from the bottom 7a and having an extended end portion projecting axially for rotatably supporting the driven rotor 12 on the extended end portion via a sleeve-like bearing 15. In the above well-known magnet pump 1, the rotation of the drive rotor 10 causes rotational driving of the driven rotor 12 to cause rotation of the impeller 6, thus causing fluid to be pumped to flow into the pump chamber 2 through the suction port 3 as shown by arrow and be sent out through the discharge port 4 as shown by arrow. In this pumping operation, the fluid in the pump chamber 2 partly flows as a circulating flow into the depth of the rear casing 7. In the circulating flow, the fluid flows into the frictional contact portions 15a defined between the sleeve- like bearing 15 integral with the driven rotor 12 and the spindle 14 from the rear end side of the bearing 15 as shown by dashed line arrows to come out to the front end side and pass through a central communication hole 16 provided in the impeller 6, thereby providing a cooling effect to suppress increased heat generation by the friction of the frictional contact portions 15a and also providing a lubricating action. In the frictional contact portions 15a, a fluid passage groove is formed, which is a helical groove or like a spline. During the pumping operation, a negative pressure prevails on the front side of the impeller 6 that faces the suction port 3, while the driven rotor section including the driven rotor 12 and the impeller 6 normally receives a thrust in the direction toward the suction port 3, i.e., in the direction toward the front. Thus, ring-like front thrust bearing 17 is provided in a front casing 5 for supporting the thrust, and a mouth ring 18 provided on the side of the impeller 6 is in frictional contact with the front thrust bearing 17. Further, a thrust may act on the driven rotor section in the direction opposite to the direction toward the suction port 3, i.e., in the rearward direction. This results from vibration of the driven rotor section in the thrust direction while the driven rotor portion remains rotating which is caused when the pump is operated idly or abnormally due to trapping of air or like cause. Thus, a rear thrust bearing member 19 for supporting the rearward thrust acted on the driven rotor section is provided on a boss 13 around the spindle 14, so that the rear end of the sleeve-like bearing 15 is in frictional contact with the rear thrust bearing member 19 in the event of the generation of a rearward thrust. As noted above, the sleeve-like bearing is brought to a state with its rear end in frictional contact with the rear thrust bearing member in the event of the idling operation of the pump or an abnormal operation thereof such as air trapping. At this time, frictional heat is generated in the frictional contact portions, and it poses a problem. More specifically, the rear thrust bearing member, unlike the front thrust bearing member, is provided in the depth of the rear casing. therefore, the diffusion of the frictional heat is inferior, and when the temperature is increased, the bearing ports are seized. Particularly, where the rear casing or like enclosure member is a synthetic resin molding, the heat has an adverse effect of causing damage to these parts due to fusing. Further, when the rear end of the sleeve-like bearing is brought into frictional contact with the rear thrust bearing member, the circulating flow entering the frictional contact portions defined around the spindle generates heat and get into circulation failure, thus making the problem more significant. To solve the problem, it has been proposed to provide a heat isolation structure adopting a heat insulating material such as to surround the frictional contact portions of the rear thrust bearing or the like. In this case, cost increase due to the provision of the heat insulation structure is inevitable. In addition, since the heat insulation material prevents diffusion of heat, the frictional contact portions are quickly elevated in temperature even by a short period of idling, and a commonly called heat shock is liable to be generated by priming fluid supplied into the pump chamber immediately afterwards. SUMMARY OF THE INVENTION An object of the present invention is to provide a magnet pump, which can greatly suppress frictional heat generation in the frictional contact portions in the event of generation of idling or like abnormal operation of the pump, has no need of providing any heat insulation structure around the frictional contact portions, permits use of a resin molding as the rear casing or like surrounding member, and permits durability improvement and cost reduction of the entire pump. This object is achieved according to the invention with a magnet pump according to Claim 1. Further, according to the invention there is provided a magnet pump in which support means for supporting said rear thrust bearing member is provided on said rear side portion of the impeller or on said front side portion of the driven rotor. Further, according to the invention there is provided a magnet pump in which either one of said rear thrust bearing member and the axial end face of the spindle has a spherically shaped contact portion, and in which said spindle is fixed at the distal end thereof and projects in a cantilever fashion. With the magnet pump with the rear thrust bearing member according to the invention, the rear thrust bearing member is disposed such that it is capable of frictional contact with the axial end face of the spindle, and the support portion for supporting the rear thrust bearing member is provided on the rear side of the impeller, or on the front side of the driven rotor. Thus, when the driven rotor and the impeller are vibrated in the thrust direction while being moved in the rearward direction, the rear thrust bearing member is brought into contact with the axial end face of the spindle in the stationary state. The rear thrust bearing member, unlike the depth of the rear casing, is disposed on the back rear side in the neighborhood of the impeller. Thus, ready heat diffusion is obtainable. In addition, a cooling effect with stirring of the impeller in the pump casing is obtainable. Thus, the heat generated by the friction between the rear thrust bearing member and the axial end face of the spindle can be diffused satisfactorily, and the temperature rise of the frictionally movable part including the thrust bearing member can be suppressed. Further, since the flow path of the circulating flow passing between the spindle and the sleeve-like bearing is not blocked. Thus, the satisfactory cooling action around and lubricating action of the spindle can be maintained. Further, the circulating flow is provided to the rear thrust bearing member as well, and thus further satisfactory heat diffusion is obtainable. Further, with the structure in which either one of the frictional contact portions of the axial end face of the spindle and the rear thrust bearing member is spherical in shape, the area of the frictional contact is reduced, and the heat generation can be reduced extremely. It is thus possible to permit a synthetic resin molding to be used as the rear casing or like surrounding member without need of adopting a heat insulation structure or like special measure. A magnet pump which is durable very much and readily permits cost reduction, thus can be provided. The above features and advantages of the invention will be more fully understood from the detailed description of the preferred embodiments when the same is read with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view, partly in section, showing a magnet pump with a specific structure of a rear thrust bearing member embodying the invention; FIG. 2 is a fragmentary enlarged-scale sectional view of a magnetic pump concerning a modification structure of the rear thrust bearing member according to the invention; and FIG. 3 is a fragmentary sectional view showing a magnet pump with a rear thrust bearing member of a prior art structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, an embodiment of the magnet pump will be described with reference to Figs. 1 and 2. Referring to Fig. 1 showing the magnet pump 20, designated at 21 is a pump body accommodating an internal drive motor (not shown). Designated at 22 is a front casing, which is mounted on the pump body, defines an inner pump chamber 23 and has suction port 24 extending in the axial direction shown as an axis X-X and a circumferentially extending discharge port 25. Designated at 26 is an impeller rotatable disposed in the pump chamber 23 and having the front side (right side in the Figure) facing the suction port 24. Designated at 27 is a ring-like front thrust bearing member provided in the front casing 22 and in frictional contact with a mouth ring 28 provided on the impeller 26. Designated at 29 is a cylindrical rear casing with a bottom, which is assembled in the pump body 21 and cooperates with the front casing 22 to enclose the pump chamber 23 fluid tight. Designated at 30 is a drive rotor disposed outside the rear casing 29, having a ring-like drive magnet 31 and receiving rotational drive torque from the drive motor in the pump body 21. Designated at 32 is a driven rotor disposed in the rear casing 29, having ring-like driven magnet 33 facing and forming a magnet coupling with the drive magnet 31 via the rear casing 29 and rotatable in unison with the impeller 26. Designated at 34 is a spindle fixed to the bottom 29a of the rear casing 29 at the distal end thereof by a boss 35 integral with and projecting from the bottom 29a and has an extended end portion 34a extending axially in a cantilever fashion. The driven rotor 32 is rotatably supported on the extended end portion 34a of the spindle 34 via a sleeve-like bearing 36. The bearing 36 is secured to the driven rotor 32 and has its frictional portion with respect to the spindle 34 formed with flow groove or in the form of splines. During the pumping in chamber 23 the fluid partly flows as a circulating flow into the depth of the rear casing 29, and as shown by dashed line arrows it enters between the frictional contact portions 36a from the rear end of the bearing 36 to provide a cooling effect and lubricating effect. At the start of the pumping operation, the drive rotor 30 is rotated with energization of the drive motor, thus causing rotation of the driven rotor 32 on the spindle 34 in unison with the impeller 26. As a result, fluid to be pumped flows through the suction port 24 into the pump chamber 23 as shown by arrow to be fed out through the discharge port 25 to a destination portion (not shown). The structure part of the magnet pump described above is the same as the prior art structure described earlier with reference to Fig. 3. As for the materials of the various parts, the impeller 26, the rear casing 29 and the driven rotor 32 are fabricated as synthetic resin moldings. The sleeve-like bearing 36, the front thrust bearing member 27, the mouth ring 28 and the spindle 35 are desirably manufactured by using ceramic materials excellent in the corrosion resistance, hardness, etc. In the embodiment of the magnet pump shown in Fig. 1, a structure part concerning the rear thrust bearing member as a feature of the invention will now be described. On the back side or rear side of the impeller 26 opposite the front side facing the suction port 24, the back center of the impeller 26 has an integral boss-like support 40, which supports a rear thrust bearing member 41 projecting along the axis line X-X. The rear thrust bearing member 41 exposed form the support 40 has a spherically shaped frictional contact portion 41a as shown, which faces a flat axial end face 42 of the spindle 34. The impeller 26 has communication holes 43 for circulating the fluid to be pumped. Each communication hole 43 is formed aside from each side of a central portion of the impeller 26 since the rear thrust bearing member 41 is disposed on the central portion. In the above construction, during the steady-state operation of the pump, the driven rotor 32 together with the impeller 26 receives a thrust directed in the direction toward the front, thus, is rotated in a state that the mouth ring 28 is brought into frictional contact with the front thrust bearing member 27. During this time, the rear thrust bearing member 41 is out of contact with the axial end face 42 of the spindle. However, when the driven rotor part is caused to undergo vibrations in the axial direction and receive a rearward thrust due to such cause as idling of the pump or air trapping, the frictional contact portion 41a of the rear thrust bearing member 41 is brought into contact with axial end face 42 of the spindle, thus receiving the rearward thrust. As the driven rotor part continues rotation in this contact state, frictional heat is generated in the frictional contact portions 41a. However, the place of generation of the frictional heat is not located in the depth of the rear casing 29 as in the prior art structure, but is found in the neighborhood of and right after the rear side of the impeller 26. Thus, the cooling effect due to stirring of the impeller 26 in the front casing 22 can be readily received. It is thus possible to obtain satisfactory heat diffusion of the frictional heat and suppress temperature rise around the frictional portions. Further, with the frictional contact portion 41a of the rear thrust bearing member 41 made to be spherical in shape, the area of frictional contact with the axial end face of the spindle is reduced, and thus it is possible to further suppress heat generation in that locality. Further, unlike the prior art structure, no rear thrust bearing member is provided between the rear end of the sleeve- like bearing 36 and the boss 35, and this gap therebetween maintained at all times even with the rear thrust bearing member 41 in contact with the axial end face of the spindle 34. Thus, as shown by the dashed line arrows, the fluid that reaches the depth of the rear casing 29 flows as a circulating flow into between the frictional portions 36a from the rear end of the bearing 36 to come out from the front end and pass through the communication holes 43 formed in the impeller 26. Thus, the cooling action and lubricating action between the sleeve-like bearing 36 and spindle 34 can be held satisfactory at all times, thus precluding the possibility of seizure or damage to these parts. Further, since the circulating flow is provided around the rear thrust bearing member 41, the heat diffusion is further promoted. Fig. 2 shows a modification structure of the rear thrust bearing member shown in the embodiment of Fig. 1. In the figure, parts like those in Fig. 1 are designated by like reference numerals. In this modification structure, a support portion for supporting the rear thrust bearing member 41 is provided, in lieu of providing on the impeller 26, on an intermediate member 44 forming the front side. The intermediate member 44 constitutes a part of the driven rotor 32. Specifically, the intermediate member 44 is cylindrical and has a bottom 44a, and it is secured to the outer periphery part of the sleeve-like bearing 36, with its bottom located between the axial end face 42 of the spindle 35 and the rear side of the impeller 26. The bottom 44a serves as the support portion, to which the rear thrust bearing member 41 is secured. In the above modification structure, the frictional contact portion 41a of the rear thrust bearing member 41 has a flat surface shape, whereas the axial end face 42 is provided with a frictional contact portion 42a having a spherical shape. With the provision of the spherical frictional contact portion on one of the mutually frictional contact portions, the above effect is obtainable. However, with the frictional contact portions both having flat surfaces, an effect which is not obtainable in the prior art is obtainable. Thus, the structure, in which the frictional portions are spherical in shape, is not limitative. The bottom 44a of the intermediate member 44 has a communication hole 45, which is communicated with a communication hole 43 which is formed in the central portion of the impeller 26. The circulating flow which gets out of the frictional parts 36a of the sleeve-like bearing 36 is circulated as shown by the dashed line, whereby the frictional heat generated in the rear thrust bearing member 41 is diffused more satisfactorily. While the embodiment of the invention and the modification structure thereof have been described in the foregoing, they are by no means limitative of the invention.

Claims: A magnet pump including a front casing (22) defining an inner pump chamber (23) and having an axially extending suction port (24) and a circumferentially extending discharge port (25), an impeller (26) rotatably disposed in the pump chamber, the impeller having a front side portion facing the suction port and a rear side portion opposite to the front side portion, a cylindrical rear casing (29) with a bottom (29a), cooperating with the front casing to enclose the pump chamber fluid tight, a drive rotor (30) disposed outside the rear casing and having a drive magnet (31), a driven rotor (32) having a driven magnet (33) facing and forming a magnet coupling with the drive magnet and rotatable in unison with the impeller which is mounted on a front side portion of the driven rotor, a spindle (34) secured to the rear casing, said spindle having an axial end face (42) at the extended end portion axially projecting toward the suction port and rotatably supporting the driven rotor and the impeller thereon, and a rear thrust bearing member (41) for supporting a rearward thrust acting on the driven rotor and the impeller in the direction opposite to the direction toward the suction port, characterized in that said driven rotor (32) and the impeller (26) are supported on said spindle (34) so as to be movable in the axial direction of said spindle, and said rear thrust bearing member (41) is disposed to be in frictional contact with said axial end face of the spindle only in the event of an idling operation or abnormal operation thereof. The magnet pump according to claim 1, in which support means (40) for supporting said rear thrust bearing member (41) is provided on said rear side portion of the impeller (26). The magnet pump according to claim 1, in which support means (44a) for supporting said rear thrust bearing member (41) is provided on said front side portion of the driven rotor (32, 44). The magnet pump according to one of claims 1, 2 and 3, in which either one of said rear thrust bearing member (41) and the axial end face (42) of the spindle (34) has a spherically shaped contact portion (41a, 42a). The magnet pump according to claims 1, 2, 3 and 4, in which said spindle (34) is fixed at the distal end thereof and projects in a cantilever fashion.

Inventors: KONDOH TOSHIHIKO, OKADA KAZUO, KONDOH, TOSHIHIKO, OKADA, KAZUO, KONDOH, TOSHIHIKO, C/O IWAKI CO., LTD., OKADA, KAZUO, C/O IWAKI CO., LTD.
Applicants: IWAKI CO LTD, IWAKI CO., LTD.
Application year: 1994
Main classification: H02K7
IPC codes: H02K5, H02K49, F04D29, F04D13, H02K7